Logical channel management in a wireless communication network

ABSTRACT

A wireless transmit/receive unit (WTRU) is configured to transmit scheduling information over a first uplink channel, on a condition that the WTRU has an uplink scheduling grant to transmit uplink data. In response to a triggering condition, when the WTRU is not transmitting on the first uplink channel, the WTRU is configured to transmit a plurality of a same value over a second uplink channel. The second uplink channel is a control channel. The transmission of the plurality of the same value is based on having an insufficient uplink scheduling grant for the first uplink channel.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/207,795 filed Dec. 3, 2018, which is a continuation of U.S. patentapplication Ser. No. 15/581,902 filed Apr. 28, 2017, which issued asU.S. Pat. No. 10,148,405 on Dec. 4, 2018, which is a continuation ofU.S. patent application Ser. No. 14/449,819 filed Aug. 1, 2014, whichissued as U.S. Pat. No. 9,641,304 on May 2, 2017, which is acontinuation of U.S. patent application Ser. No. 12/942,528 filed Nov.9, 2010, which issued as U.S. Pat. No. 8,797,873 on Aug. 5, 2014, whichis a continuation of U.S. patent application Ser. No. 11/840,308 filedAug. 17, 2007, which issued as U.S. Pat. No. 7,830,835 on Nov. 9, 2010,which claims the benefit of U.S. Provisional Application Ser. No.60/839,198 filed Aug. 21, 2006, the contents of which are each herebyincorporated by reference herein.

FIELD OF INVENTION

The present invention is related to high speed uplink packet access(HSUPA) wireless communication systems. More particularly, the presentinvention is related to a method and apparatus for preventingtransmission blocking in an HSUPA wireless communication system.

BACKGROUND

The Third Generation Partnership Project (3GPP) Release 6 defines fastcontrol of wireless transmit/receive unit (WTRU) transmissions throughNode-B based scheduling in HSUPA. This faster control results in bettercontrol of the uplink (UL) noise rise, which allows operation at ahigher average UL load without exceeding the threshold, therebyincreasing system capacity. In HSUPA, control and feedback occursthrough different physical control channels and information elements(IEs).

Node-B commands are conveyed by absolute or relative grant channels,while WTRU feedback is transmitted on an enhanced dedicated physicalcontrol channel (E-DPCCH), or “happy bit” within the E-DPCCH, wherescheduling information (SI) is appended to the payload. The Node-Bcommands are expressed by a maximum power ratio over the power of the ULcontrol channel (DPCCH). The happy bit is transmitted within the E-DPCCHalong with 2 bits for retransmission sequence number (RSN) and 7 bitsfor the enhanced transport format combination indication (E-TFCI). Allcombinations of the 7 E-TFCI bits are defined to mean a specific size ofthe enhanced transport format combination (E-TFC). The value “0” (7bits) is defined to mean the transmission of the SI alone. The E-DPCCHis always transmitted along with the enhanced dedicated physical datachannel (E-DPDCH) except during compressed mode. Transmission of E-DPCCHalone does not occur.

The WTRU and Node-B are aware how much data can be transmitted for agiven power ratio, and this correspondence is controlled by the radionetwork controller (RNC). Such a scheduled operation is particularlywell suited to non-delay-sensitive types of applications, however it mayalso be used to support more delay-sensitive applications, given thefast resource allocation capabilities.

Under the current standard, data is optionally segmented, and bufferedat the radio link control (RLC) layer. The set of possible RLC packetdata units (PDU) sizes that are delivered to the medium access control(MAC) layer is configured by radio resource control (RRC) signaling.When segmentation takes place, generally the sizes of the PDUs areconfigured to be of the order of several hundreds of bits to avoidexcessive overhead and obtain good coding performance. Currently, thereis no further segmentation at the MAC layer. Accordingly, when a newtransmission takes place, an integer number of PDUs, including zero,must be sent.

Since it is not possible to send out a fraction of an RLC PDU, a certainminimum instantaneous bit rate for the WTRU transmission is imposed. Forinstance, if the PDU size is 320 bits and the transmission time interval(TTI) is 2 milliseconds (ms), the instantaneous bit rate needs to be atleast 160 kilobits per second (kbps), without accounting for MACoverhead. Such an instantaneous bit rate translates into a certainminimum transmission power ratio, under which no RLC PDUs can be sent.

During scheduled operation, WTRU transmissions from a given MAC-d flowcan be completely interrupted, or “blocked,” if the granted power ratiofalls under the minimum required to transmit the RLC PDU at the head ofbuffer. Such a situation may occur out of the control of the servingradio link set, (i.e., Node-B) for a number of reasons. For example, theWTRU may have received a non-serving relative grant requesting adecrease of power from another Node-B, the WTRU may have erroneouslydecoded a relative or absolute grant command from the serving Node-B, orthe WTRU may have several different configured RLC PDU sizes on a givenMAC-d flow and a bigger than usual RLC PDU size is up for transmission.

When such a situation occurs, the WTRU cannot transmit until the time itis scheduled to transmit an SI. Until then, and unless the previous SIhas been transmitted recently enough for the Node-B to infer that theWTRU buffer is not empty based on its subsequent transmissions, theNode-B has no ability to determine whether transmission stopped becausethe power ratio fell under the minimum, or simply because the WTRU hasnothing to transmit. Accordingly, transmission from the WTRU is delayeduntil the SI can be transmitted.

This issue imposes a configuration of a small periodicity of SItransmission (T_SIG) for delay-sensitive applications, therebyincreasing overhead. Furthermore, even if the Node-B was aware thattransmission stopped because the power ratio is too low, when multipleRLC PDU sizes are configured, the Node-B does not know what power ratioto apply to correct the situation. Thus, the Node-B has to find out bytrial and error what the correct power ratio is. This results ininefficient resource allocation and/or excessive scheduling delays.

In the current state of the art, transmission of scheduling information(SI) is only allowed under certain conditions such as those described in3GPP TS 25.321, such as if the user has a grant (power ratio) of zero orhas all its processes de-activated and has data to transmit, upon achange of E-DCH serving RLS (base station), or periodically, with aconfigurable period depending on whether the user has a grant or not.Accordingly, a solution to prevent blocking that would be compatiblewith the mechanisms defined in the current state of the art may includeconfiguring periodic reporting of the SI with a very low period, suchthat the SI is transmitted along with almost every transmission of newdata. However, overhead may be significantly increased since each SItakes up 18 bits. For instance, assuming a MAC service data unit (SDU)size of 280 bits and a MAC-e header size of 18 bits, this wouldrepresent an additional overhead of approximately 6%.

It would therefore be beneficial to provide a method and apparatus fortransmission blocking in an HSUPA wireless communication system that isnot subject to the limitations of the current state of the art.

SUMMARY

The present invention is related to a method and apparatus forpreventing transmission blocking. Transmission of scheduling information(SI) when transmission of a medium access control-d (MAC-d) flow isstopped. The SI is transmitted when the triggering condition is met.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding of the invention may be had from thefollowing description of a preferred embodiment, given by way of exampleand to be understood in conjunction with the accompanying drawingswherein:

FIG. 1 is a functional block diagram of a WTRU and a Node-B, configuredin accordance with the present invention;

FIG. 2 is a flow diagram of a method for preventing transmissionblocking in an HSUPA wireless communication system in accordance withthe present invention;

FIG. 3 is a flow diagram of a method for preventing transmissionblocking in an HSUPA wireless communication system in accordance withanother embodiment of the present invention; and

FIG. 4 is a flow diagram of a method for preventing transmissionblocking in an HSUPA wireless communication system in accordance withanother embodiment of the present invention.

DETAILED DESCRIPTION

When referred to hereafter, the terminology “wireless transmit/receiveunit (WTRU)” includes but is not limited to a user equipment (UE), amobile station, a fixed or mobile subscriber unit, a pager, a cellulartelephone, a personal digital assistant (PDA), a computer, or any othertype of user device capable of operating in a wireless environment. Whenreferred to hereafter, the terminology “base station” includes but isnot limited to a Node-B, a site controller, an access point (AP), or anyother type of interfacing device capable of operating in a wirelessenvironment.

FIG. 1 is a functional block diagram 100 of a WTRU 110 and NB 120configured in accordance with the present invention. As shown in FIG. 1, the WTRU 110 is in communication with the NB 120 and both areconfigured to perform a method for preventing transmission blocking inan HSUPA wireless communication system in accordance with the presentinvention.

In addition to the components that may be found in a typical WTRU, theWTRU 110 includes a processor 115, a receiver 116, a transmitter 117,and an antenna 118. The processor 115 is configured to perform a methodfor preventing transmission blocking in an HSUPA wireless communicationsystem in accordance with the present invention. The receiver 116 andthe transmitter 117 are in communication with the processor 115. Theantenna 118 is in communication with both the receiver 116 and thetransmitter 117 to facilitate the transmission and reception of wirelessdata.

In addition to the components that may be found in a typical Node-B, theNB 120 includes a processor 125, a receiver 126, a transmitter 127, andan antenna 128. The processor 115 is configured to perform a method forpreventing transmission blocking in an HSUPA wireless communicationsystem in accordance with the present invention. The receiver 126 andthe transmitter 127 are in communication with the processor 125. Theantenna 128 is in communication with both the receiver 126 and thetransmitter 127 to facilitate the transmission and reception of wirelessdata.

FIG. 2 is a flow diagram of a method 200 for preventing transmissionblocking in an HSUPA wireless communication system in accordance withthe present invention. In the present embodiment of the presentinvention, new conditions for the transmission of the SI are created. Instep 210, a trigger condition for transmitting an SI is detected. Forexample, the transmission of the SI alone may occur when thetransmission of any, or in a specifically defined, MAC-d flow is stoppedbecause the current non-zero grant is smaller than the minimum requiredto transmit the next MAC SDU, or RLC PDU, of the particular MAC-d flow.The trigger condition, in this case, may occur when it is not possibleto transmit a single PDU of a given MAC-d flow. Preferably, a MAC-d flowis a group of logical channels that may be identified, or specified,with an index.

Once the trigger condition is determined, a particular WTRU 110transmits the SI (step 220). This transmission may occur once when thetriggering condition is met and periodically thereafter, (e.g. over aconfigurable period), or the transmission may occur at any time thetriggering condition occurs. Additionally, the list of MAC-d flowssubject to triggering the transmission of SI due to blocking may besignaled by higher layers, as well as the configured periodicity oftransmission once the condition is met.

FIG. 3 is a flow diagram of a method 300 for preventing transmissionblocking in an HSUPA wireless communication system in accordance withanother embodiment of the present invention. In step 310, a triggercondition is detected. Preferably, the trigger condition met in step 310is substantially similar to the trigger conditions described in step 210of method 200 above. However, unlike the method 200, when the triggercondition is detected in step 310, instead of transmitting the SI,nothing is transmitted on the E-DPDCH and all 10 bits of the E-DPCCH areset to a value of zero “0” (step 320).

In effect, this corresponds to the same setting as for the initialtransmission of an SI alone, except that the SI is not actuallytransmitted. An advantage of this technique is that the requiredtransmission power may be lowered further than if the SI is actuallytransmitted. However, the E-DPCCH should be transmitted at a value highenough for the network to detect that something has been transmitted onthe E-DPCCH. Additionally, less information may be available to thenetwork about the status of the buffer in the WTRU 110.

FIG. 4 is a flow diagram of a method 400 for preventing transmissionblocking in an HSUPA wireless communication system in accordance withanother embodiment of the present invention. In the present embodimentof the invention, improved feedback indicating minimum power ratio orMAC SDU size is utilized.

In the current state of the art, the possible MAC SDU sizes, orequivalently RLC PDU sizes, are configured upon radio bearer setup orreconfiguration through RRC signaling. The NB 120 is also aware of thePDU sizes through NB application part (NBAP) signaling. The power ratiogrant required to transmit an E-TFC (MAC-e PDU) of a certain size isknown by the WTRU 110, NB 120 and RNC, and any modification is signaledthrough RRC/NBAP signaling. Thus, using information available with thecurrent standard, the NB 120 could determine what power ratio isrequired to transmit an E-TFC containing a single RLC PDU for eachconfigured RLC PDU size.

By utilizing the signaling defined in the current standard, the NB 120may reduce the frequency of occurrence of the issue by never signaling apower ratio to the WTRU 110 that is lower than what is required totransmit the largest RLC PDU size among the RLC PDU sizes configured. Itmay, however, still be possible that the WTRU 110 blocks transmissionbecause it received a “down” non-serving relative grant or because itmisinterpreted a serving grant. The NB 120 should assume the largest RLCPDU because it is not aware of the size of the next RLC PDU in line fortransmission at the WTRU's side. As soon as there is more than one RLCPDU size configured, the NB 120 over-allocates resources for the WTRU110 whenever it is using one of the smaller RLC PDU sizes.

Accordingly, a new type of control information may be signaled by theWTRU 110 to the NB 120, so that the NB 120 may be aware of the minimumpower ratio that should be granted to the WTRU 110 with respect to thesize of an upcoming RLC PDU buffered for transmission. This information,preferably, may be referred to as the minimum grant information (MGI).

In step 410 of the method 400, the MGI is set. The setting of the MGImay be accomplished in a number of ways. For example, the MGI may be setto the size of the next RLC PDU in line for transmission, (i.e., afterthe current E-TFC is transmitted), on one of the highest priority MAC-dflows having data in its buffer, or on specific MAC-d flows that may beconfigured by RRC signaling. Additionally, the MGI may be set accordingto the size of the largest buffered RLC PDU of the highest priorityMAC-d flow. Also, the MGI may be set according to the size of thelargest buffered RLC PDU of the highest priority MAC-d flow, or onspecific MAC-d flows, expected to be transmitted by a certain delay withthe current grant and number of active processes. The delay may be alsobe configured by RRC signaling.

After determining that the MGI should be transmitted, the MGI is thenencoded (step 420). An “upcoming RLC PDU” may be used to describe an RLCPDU that has its size used for setting the value of fields of the MGI.The MGI may then be encoded according to a variety of methods. Forexample, the MGI may be encoded to consist of 5 bits and represent apower ratio with a mapping, such as bit mapping, similar to that foundin the 3GPP TS 25.212 specification. In this case, the signaled powerratio will be the smallest value that allows transmission of theupcoming RLC PDU.

Alternatively, the MGI may be encoded by a smaller number of bits andrepresent a power ratio. However, in this case, the mapping may bedifferent and have a lower granularity than the mapping found in the3GPP TS 25.212 specification. For example, the MGI may be encoded withless than 5 bits as described above. Additionally, the mapping might bepre-established.

In another alternative, the MGI may consist of a variable number of bitsdepending on how many potential RLC PDU sizes should be represented. Forinstance, in case there are 4 configured RLC PDU sizes, 2 MGI bits wouldbe required, and each combination would represent a specific RLC PDUsize. It should be noted that not all configured RLC PDU sizesnecessarily need to be mapped. Accordingly, in case only a subset of RLCPDU sizes is mapped, the WTRU 110 sets the MGI according to the smallestRLC PDU size larger than the upcoming RLC PDU.

The MGI is then transmitted by the WTRU 110 (step 430). The triggeringof the MGI may occur in one of several ways. For example, the MGI may betransmitted once whenever its value would change in accordance with theMGI settings. Also, the MGI may be transmitted at each of a particularnumber (N) of new MAC-e transmissions, where N is configurable by theradio resource controller (RRC). Additionally, it may be required thattwo consecutive transmissions of the MGI are separated by a delay of atleast a particular number (M) transmission time intervals (TTI), where Mis also configurable by the RRC.

Once transmitted, the MGI is received and decoded by the NB 120 (step440) preferably at the same time as a MAC-e PDU, and the NB 120 makesadjustments based upon the MGI (step 450). Preferably, the NB 120adjusts the power ratio to enable transmission of the upcoming RLC PDUbuffered for transmission.

In another embodiment of the present invention, the data rate is managedthrough the use of a scheduling grant. In this embodiment, thetransmission is allowed for a minimum number of PDUs (N_(min)) of theMAC-d flow for every new MAC-e transmission, without regard to the datarate imposed by the power ratio and without regard to the size of thePDU or PDUs.

Under the current 3GPP standard, (e.g., TS 25.309 Release 6), a MAC-dflow is managed through either non-scheduled transmissions or scheduledgrants, but not both. Utilizing non-scheduled transmissions for a givenMAC-d flow would overcome problems in the current art for this MAC-dflow, at the expense of a loss of control over the amount ofinterference generated by this flow.

However, in the present hybrid scheduled/non-scheduled embodiment of theinvention, the benefit of scheduling grants in terms of noise risestability is maintained while ensuring that transmission is nevercompletely blocked due to the granted power ratio falling under thethreshold for single PDU transmission. The N_(min) that is allowed for anew transmission may be set through RRC signaling.

If the required power ratio to transmit the N_(min) PDUs is higher thanthe current grant, several options may be employed. Preferably, thepower ratio is allowed to increase above the current grant to supportthe transmission of the PDUs. However, the power ratio may also stay atthe current grant, with the WTRU 110 selecting the minimum E-TFC thatcan support the N_(min) PDUs. Since more data is transmitted in thisscenario for the same power, more hybrid automatic repeat request (HARQ)retransmissions for this MAC-e PDU will be required.

For example, assuming that a MAC-d flow has two configured RLC PDUsizes, 300 and 600 bits, a minimum power ratio required to transmit aMAC-e PDU may be assumed to be (47/15)² if it contains 2 RLC PDUs of 300bits and (53/15)² if it contains a single RLC PDU of 600 bits. In ascenario where the PDU size of 300 bits is transmitted most of the timeand the 600 bits is encountered infrequently, the power ratio granted tothe WTRU 110 might be maintained at (53/15)² on the activated HARQprocesses for WTRU 110. When an RLC PDU of 600 bits shows up at the headof the buffer, under the current standard with the MAC-d flow managed byscheduling grant, the transmission would block. With the hybridnon-scheduled/scheduled solution of the present embodiment of theinvention, the WTRU 110 would be allowed to transmit its MAC-e PDUcontaining the RLC PDU of 600 bits and transmission would not beinterrupted. For this MAC-e transmission, either the interference mightbe slightly higher than planned or there might be a higher probabilityof more HARQ retransmissions, depending on whether the power ratio isallowed to increase above the current grant or not.

Although the features and elements of the present invention aredescribed in the preferred embodiments in particular combinations, eachfeature or element can be used alone without the other features andelements of the preferred embodiments or in various combinations with orwithout other features and elements of the present invention. Themethods or flow charts provided in the present invention may beimplemented in a computer program, software, or firmware tangiblyembodied in a computer-readable storage medium for execution by ageneral purpose computer or a processor. Examples of computer-readablestorage mediums include a read only memory (ROM), a random access memory(RAM), a register, cache memory, semiconductor memory devices, magneticmedia such as internal hard disks and removable disks, magneto-opticalmedia, and optical media such as CD-ROM disks, and digital versatiledisks (DVDs).

Suitable processors include, by way of example, a general purposeprocessor, a special purpose processor, a conventional processor, adigital signal processor (DSP), a plurality of microprocessors, one ormore microprocessors in association with a DSP core, a controller, amicrocontroller, Application Specific Integrated Circuits (ASICs), FieldProgrammable Gate Arrays (FPGAs) circuits, any other type of integratedcircuit (IC), and/or a state machine.

A processor in association with software may be used to implement aradio frequency transceiver for use in a wireless transmit receive unit(WTRU), user equipment (UE), terminal, base station, radio networkcontroller (RNC), or any host computer. The WTRU may be used inconjunction with modules, implemented in hardware and/or software, suchas a camera, a video camera module, a videophone, a speakerphone, avibration device, a speaker, a microphone, a television transceiver, ahands free headset, a keyboard, a Bluetooth® module, a frequencymodulated (FM) radio unit, a liquid crystal display (LCD) display unit,an organic light-emitting diode (OLED) display unit, a digital musicplayer, a media player, a video game player module, an Internet browser,and/or any wireless local area network (WLAN) module.

What is claimed:
 1. A method, implemented by a wireless transmit/receiveunit (WTRU), the method comprising: receiving a first downlink controlinformation indicating that the WTRU is to transmit uplink data on afirst uplink channel; receiving an indication of logical channels thatare subject to triggering of an uplink scheduling request; transmittinga plurality of a same value over a second uplink channel in response toa triggering condition, wherein the triggering condition is based on thereceived indication of logical channels, wherein the second uplinkchannel is a control channel; and receiving a second downlink controlinformation in accordance with the transmitted plurality of the samevalue over the second uplink channel.
 2. The method of claim 1, whereinthe transmitting the plurality of the same value is in response to thefirst downlink control information providing an insufficient amount totransmit data over the first uplink channel.
 3. The method of claim 1,further comprising transmitting, for a logical channel, an indication ofa recommended uplink resource.
 4. The method of claim 3, wherein theindication of the recommended uplink resource is associated with a datarate.
 5. The method of claim 3, further comprising receiving an uplinkscheduling resource for the first uplink channel based on thetransmitted indication.
 6. The method of claim 1, wherein thetransmission of the plurality of the same value is a request for anuplink scheduling resource.
 7. A wireless transmit/receive unit (WTRU)comprising: a processor; a receiver; and a transmitter; wherein: theprocessor and the receiver are configured to receive a first downlinkcontrol information indicating that the WTRU is to transmit uplink dataon a first uplink channel; the processor and the receiver are furtherconfigured to receive an indication of logical channels that are subjectto triggering of an uplink scheduling request; the processor and thetransmitter are configured to transmit, in response to a triggeringcondition, a plurality of a same value over a second uplink channel,wherein the triggering condition is based on the received indication oflogical channels, wherein the second uplink channel is a controlchannel; and the processor and the receiver are further configured toreceive a second downlink control information in accordance with thetransmitted plurality of the same value over the second uplink channel.8. The WTRU of claim 7, wherein the transmission of the plurality of thesame value is in response to the first downlink control informationproviding an insufficient amount to transmit data over the first uplinkchannel.
 9. The WTRU of claim 7, wherein the processor and thetransmitter are further configured to transmit, for a logical channel,an indication of a recommended uplink resource.
 10. The WTRU of claim 9,wherein the indication of the recommended uplink resource is associatedwith a data rate.
 11. The WTRU of claim 9, wherein the receiver isfurther configured to receive an uplink scheduling resource for thefirst uplink channel based on the transmitted indication.
 12. The WTRUof claim 7, wherein the transmission of the plurality of the same valueis a request for an uplink scheduling resource.